Evaluation of strengthening behavior of Al–AlN nanostructured composite by the use of modified Heckel model and response surface methodology

Abstract

Al–AlN powder mixtures with 0, 5 and 10wt.% of AlN were mechanically alloyed in a planetary ball mill under argon atmosphere up to 25h. The compressibility behavior of the obtained samples was investigated in a wide range of compaction pressure from 62.5 up to 875MPa. It was shown that presence of 10wt.% of AlN leads to a reduction in the rate of hardening after 15h milling. The morphological features of the samples showed that after 15 and 25h milling, a relative steady-state equiaxed powder can be synthesized in the case of Al–10% AlN and Al–5% AlN, respectively. A combined modified Heckel model and response surface methodology (RSM) based on central composite design (CCD) was also employed to study the effect of three factors of AlN wt.%, milling time and compaction pressure on the densification and strengthening behavior of nanostructured Al–AlN composites. All the three factors had statistically significant effect on density (D) and yield strength (YS); while in the case of milling strengthening fraction (MSF) as the response, AlN was statistically insignificant. Second order polynomial models were successfully fitted to the responses in different ranges of low (125–375MPa) and high (625–875MPa) pressures. Furthermore, the statistically significant interactions between parameters were comprehensively discussed in each case.